A heterogeneous network (HetNet) is an appealing solution for providing increased capacity to mobile users and is expected to be widely deployed in the near future. The HetNet comprises various types of cells, such as macro cells, pico cells and femto cells. In a typical layout, a macro base station provides a wide area coverage serving users within the macro cell. Within the macro cell there will be areas with high amount of traffic, i.e. high concentration of users, and areas lacking coverage (coverage holes). In those areas it would be desirable to deploy additional capacity to keep user satisfaction. In the HetNet, the added capacity is provided by deploying access nodes within the macro cell in order to concentrate a capacity boost to a smaller area, in which the capacity is needed. Such access nodes, e.g. a pico base station (of the pico cell) or a femto base station (of the femto cell), typically have lower output power and thus cover a smaller area. In the HetNet scenario, the macro base station can be seen as providing coverage while femto or pico base stations provide capacity.
In the HetNet there is a multitude of signals transmitted in the various cells. These signals cause interference, which in turn may lower the throughput performance in the HetNet and various techniques aimed at reducing interference are available. Common Reference Symbol (CRS) interference cancellation is one such technique providing one way of increasing the throughput by removing an interfering CRS signal of a neighboring cell from a received signal of a serving cell.
An estimation of interference may thus take into account the CRS interference cancellation in order to improve the accuracy of the interference estimation. There are other sources of interference as well, besides the CRS interference from other cells. The accuracy of an interference estimate affects the ability of the user equipment to decode received signals and it is thus desirable to provide as accurate interference estimates as possible.